The present invention relates to a unit for feeding flat diecut blanks of wrapping material to a user machine.
In particular, the invention relates to a unit by which flat cardboard blanks are fed to a wrapping machine, and reference is made directly in the following specification, albeit with no limitation implied, to cartoner machines for packaging ordered groups of articles such as bottles or other similar containers.
The prior art embraces feed units of the general type comprising an intermittently driven conveyor belt on which flat cardboard blanks ordered in a substantially continuous file or column are caused to advance longitudinally along a rectilinear and substantially horizontal path that extends toward a transfer station where they are taken up singly and in succession from the advancing column by a pickup mechanism. The blanks making up the column are set on edge, lying transversely to the feed direction, and breasted one with another in such a way as to form a compact mass on the conveyor.
In units of the type in question, the conveyor is indexed through a step equivalent to the thickness of a single blank, synchronously with the operation of the pickup mechanism, which in turn is activated cyclically and synchronously with the working parts of the cartoner.
The leading blank of the column, or in effect the blank which at any given moment precedes the others in the feed direction, is engaged at the transfer station by a retaining device serving to maintain the compactness of the column. Generally speaking, the retaining device comprises at least one detent element positioned to interact with a point on the periphery of the blank, whilst the pickup mechanism consists in suction cup means positioned to engage a substantially central portion of the blank. This means that when subjected to the combined action of the detent and the suction pickup mechanism, the blank is caused to flex elastically in such a way that it can slip free of the detent.
The blanks generally are placed on the conveyor in ordered packs by the machine operator.
Accordingly, the storage capacity of the conveyor for a selected operating speed of the machine must be sufficient to ensure that the supply of blanks on the conveyor at any given time is not depleted before the operator has had time to load a new pack.
As the operating speed of cartoners has continued to increase, conveyors of correspondingly larger capacity have continued to be developed: or rather, additional capacity has been gained through the simple expedient of elongating the conveyors along the direction followed by the blanks.
It happens, however, that when a conveyor of the type described above is increased in length this also has the effect of raising the maximum value of inertia-related stresses set up in the structure of the conveyor by the intermittent motion transmitted to the column of blanks. In this type of conveyor, accordingly, increased storage capacity needs to be accompanied by greater strength, which clearly must involve higher construction costs.
The object of the present invention is to provide a feed unit for flat diecut blanks which, compared with those of the prior art, affords a relatively large storage capacity and at the same time will be relatively simple and economical in embodiment.